Big-Block Nitrous System - The Coolest Squeezin' Rat

Testing The New EFI NOSzels From NOS

For a long time spraying lots of "dry" nitrous into an electronically fuel-injected engine involved complicated plumbing and fuel pressure issues, and swapping in some very big fuel injectors to add the proper amount of fuel at the proper time. Unfortunately, big injectors don't like driving at part throttle, and most cars equipped with them became temperamental on the street. NOS has changed all that with its new NOSzels EFI nitrous system. The NOSzels are a unique type of fogger nozzle that is installed between the fuel injector and the intake manifold bung. When the nitrous system is turned off, the engine's fuel injectors work just like normal. When the system is activated, the nitrous spray helps to further atomize the injector's fuel, adding more power to the engine than just the nitrous/fuel spray would alone. Since the NOSzels are a "wet" system and spray their own fuel, there's no longer a need to install huge injectors or increase your fuel pressure when you hit the button.

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Very simple in design, the NOSzels get installed between the fuel injector and the intake manifold. The theory is that the nitrous spray will help better atomize the injector's fuel. The power we made seems to prove the point.

Back in the November '02 issue we showed you the buildup and dyno test of an engine affectionately known around the office as "The Coolest Rat." This Rat was deemed "coolest" because it had no trouble cranking out more than 615 hp and 580 lb-ft of torque, all below 6,000 rpm on pump gas, and it idled at 700 rpm! However, being the horsepower junkies that we are, all that was still not enough, and we thought a shot of NOS would be the next coolest bolt on. Luckily for us, the folks at Holley Performance Products-the makers of NOS-are just as addicted to horsepower as we are, and they had just what the our EFI'd Rat needed.

After installing and thoroughly testing the NOSzels, we are convinced that they're one of the coolest bolt-ons we've tried. The installation was simple-although it did take quite a long time because there are so many fittings to install-and tuning it was extremely easy. In fact, when comparing the NOSzels to normal-style fogger systems we've run in the past, things like jet changes are simpler with the new NOSzels, and working with the high-pressure plastic tubing was easier than working with steel lines (although some folks are not sold on the looks of the plastic lines; they like polished stainless). On a scale of 1-10 we would rate the NOSzels in the 9s. Not only did the system perform better than expected (it made as much as 50 more horsepower-350 hp at the 300hp setting-than NOS claimed it would), but it was so simple to use that we felt very confident when the time came to hit the button. Also, check out how amazingly close the extra power was to NOS's estimation. Example: the NOSzels added 103 average hp at the 100hp setting, 171 average hp at the 175hp setting, and 342 average hp at the 300hp setting!!! When NOS says you'll get an extra 100 or 200 hp with its kit, you can bet you're getting exactly that or more! While the total cost of the system is a bit on the high side for a nitrous kit (around $1,500 last time we checked Jeg's Web site for NOS PN 8008), there aren't too many people that might buy this kit who haven't already spent at least five times that on their engine. And for the money, there's still very little else on the market than can add this much bang for the buck. If you've built a serious EFI motor and are anxious to top it off with the newest in high-tech power adders, then the NOSzels could be the next best bolt on for you.

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Big-Block Nitrous System - The Coolest Squeezin' Rat

Very simple in design, the NOSzels get installed between the fuel injector and the intake manifold. The theory is that the nitrous spray will help better atomize the injector's fuel. The power we made seems to prove the point.

We had to fabricate these 1/8 x 1 x1 1/2-inch-long aluminum spacers to raise the fuel rails. We tapped the hole on top so we could reuse the original fasteners. The front of the bracket can be better seen behind the injector wires in the previous photo.

To properly orient the solenoids and brackets, we trial-fitted everything by hand after disassembling the solenoids to make them easier to work around.

You'll need a roll of Teflon tape. There are a lot of threads to seal in this kit, so be patient. Always wrap the tape around the threads counter-clockwise, or by twisting the fitting clockwise, as if you were threading it into something.

We used a 1/4-inch drive ratchet and socket to tighten the brass compression fittings. There are 16 of these fittings, so the ratchet made the job go much quicker. It's hard to strip fittings with the small 1/4-inch drive as well.

Since the ferrule has to compress to make the seal, this connection must be made tight the first time, but not too tight or you'll strip the fitting. It wasn't hard to get a feel for the proper tightness after the first fitting was snugged up.

Always use two wrenches to tighten the fittings. We also prefer to use Craftsman "stubby" wrenches to avoid stripping the soft aluminum fittings. Be sure to properly orient each fitting so you can thread all of the connections into it without interference.

The NOS "funnel" jet is unlike traditional nitrous jets. The high-pressure plastic tube slips firmly inside of it and uses a compression ferrule and nut to seal. Double check your tube lengths and routing before assembling the fitting because you've only got one chance to get it right.

We left the other wrench out of this photo so you could see the fittings better. The short Craftsman stubby wrenches really came in handy when installing this kit. We had no trouble stripping any fittings and had no leaks either.

To clear the valve covers we faced each of the NOSzels 180 degrees apart. The nice thing about the NOSzels is that, when installed, they can still swivel so it's easy to get to the fittings for jet changes.

We mounted the nitrous solenoids in front and ran the dual -6 AN lines under the intake manifold for a clean look. The lines connect with a "Y" fitting, included in the kit, under the manifold so only one -6 AN line goes to the bottle.

With our installation complete we bolted the Coolest Squeezin' Rat onto Vrbancic Brother's DTS dyno to see if the NOSzels are worth the effort. The short answer is a big YES!

Last time we dyno'd this Rat, it pulled almost 2.5 inches of vacuum at WOT, which meant the throttle body was too small, so we installed this trick Accufab throttle body this time. Note also the 1-inch carb spacer we added to raise the throttle body up so its linkage would clear the raised fuel rails.

When it was time to hit the button, we went from 91-octane pump gas to 110-octane VP Racing fuel for the 100- and 175hp NOS pulls. Then we ran C-16 VP race gas for the 300hp NOS pulls.

Since Holley's inline EFI fuel pump could not provide enough fuel to feed the engine and nitrous combined, Vrbancic used this Product Engineering pump and matching regulator. It had no trouble feeding the engine and nitrous system at a constant 43-45 psi.

Checking flowing fuel pressure with any nitrous system is critical. The NOSzels use a -4 AN fuel line, so we made this -4 to -3 AN adapter by slicing the tapered end off the -3 side in a lathe and securing the proper jet with a -3 nut. Then we turned on the fuel pump and set the pressure to the recommended 43 psi with the gas flowing into a 1-gallon can.

Instantly spraying 300-plus-hp worth of nitrous is hard on the engine's bottom end. We prefer to use NOS's Progressive Nitrous Controller and gradually bring the system up to full power in about 1.5 seconds. To the left you can see the Commander 950 ECU for the Holley MPI fuel injection system.